1. Field of the Invention
This invention relates to the field of filter cartridges, elements, and complete filters for fluids flowing in hydraulic motors or apparatuses, and in particular to those filters whose elements need to be replaced from time to time.
2. Description of the Related Art
Fluid filters are used in a wide variety of applications. For example, in the automotive and general engine industry, they are used to filter fuel, coolant, oil and other lubricants, water, and other fluids, in various components of the engine. One example of a filter might be a typical cylindrical filter cartridge composed of a filter medium that can be constructed of, e.g., paper, cardboard, felt, melt-spun, or other media, often a material which can be incinerated when the element is replaced to reduce waste. End plates typically constructed of plastic, are usually joined to the element.
Such filter cartridges are installed inside filter feed troughs or housings, often in such a way as to cooperate with a center tube or standpipe, which can consist of one or more pieces. In order to ensure sealing during filtration, elastomeric sealing rings are often arranged between center tube and flanges.
Problems often arise during replacement of the element/cartridge, given that fluid still resides in the filter housing and in empty volumes within the cartridge (such as the hollow center of a cylindrical element) and in the element media itself. This often results in dripping when the element is removed, splashing of fluid when a new cartridge is installed, and mixture of dirty fluid with clean fluid.
The present state of the art yields some designs in which the filter opens a port or valve to allow fluid to drain out of the housing when the filter is removed. The drained fluid flows to another reservoir, such as the fuel tank, oil sump, coolant reservoir, etc. One problem with current designs is a slow drain rate and expense of the large gaskets or complex valves needed to implement the system. A design is needed in which the drain rate is increased through a more open flow path, at reduced cost and complexity.